package nowcoder;
/**
 * 题目ID：45840-不要二
 * 链接：https://www.nowcoder.com/practice/1183548cd48446b38da501e58d5944eb?tpId=85&&tqId=29840&rp=1&ru=/activity/oj&qru=/ta/2017test/question-ranking
 */
import java.util.*;
public class Day06_1 {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int w = input.nextInt();
        int h = input.nextInt();
        int[][] s = new int[w+2][h+2];
        int count = 0;
        for (int i = 0; i < w; i++) {
            for (int j = 0; j < h; j++) {
                if(s[i][j] == 0){
                    count ++;
                    s[i+2][j] = 1;
                    s[i][j+2] = 1;
                }
            }
        }
        System.out.println(count);
    }
}
